The field of art to which the present invention pertains relates to a drying air control method in an automatic developing machine and an automatic developing machine employing the method, applied to a developing machine that develops silver halide photosensitive materials. To describe in more detail, the invention relates to an optimum drying air control method and a developing machine employing the method which develops original color films consisting of three or four plates used in multicolor printing.
The prior art to which the invention is directed is explained as follows.
A conventional silver halide photosensitive material which will be called a film in this specification hereafter has the characteristic that it shrinks when the humidity is low and expands when it is high. Apart from shrinkage and expansion of a film according to the humidity, a film has the characteristic that the size of a film varies before and after being processed. This means that the size of a film and the image size on the film which is equal to the size of the original plate may be different from the size of a processed film and that of the image on it. The variation in size is influenced by the temperature and humidity when the film is exposed and also when it is dried after being processed. In the latter case, the size of an original plate differs from that of a duplicated film. As a result, it causes problems which are described as follows.
Especially originals for multicolor printing consist of three original plates which are cyan, magenta and yellow or four original plates wherein black is added to those three colors. That is the reason why stability of film size is required in a set of original films. Films on the market for use as original films for multicolor printing have the above-mentioned characteristic with regard to temperature and humidity,so variation in film size before and after development is caused by variations of temperature and humidity during the exposure process and the drying process, and can be a problem in many cases.
For instance, in the case that a film exposed as a cyan plate is used as an original film, the picture position of a magenta plate is adjusted to it, and When exposure and development operations are conducted, a gap is created between the magenta plate and cyan plate.
In the case of conventional automatic developing machines, several methods to control drying air are publicly known, such as changing the recycling ratio of drying air, which means the ratio of the dry air recycling in the drying unit to the new air introduced from the outside into the unit, setting temperature gradient from the exit to the entrance of the drying unit, dehumidifying the air to be used for drying and the like. But the objectives of these methods are to increase efficiency of air drying, labor saving, energy saving, preventing uneveness of air drying, and so forth. Stability of film size has never been taken into consideration as far as these methods are concerned.
Accordingly, it is the object of the present invention to take countermeasures against these problems.
The problems to be solved by the invention are described as follows.
(A) The method of changing the recycling air ratio in accordance with the outside air humidity, has difficulty to unify the humidity of the air inside the drying unit without the influence of the humidity of the outside air, so it is impossibe to control film size stability before and after processing.
(B) The method of setting a temperature gradient is useful for increasing drying efficiency, but fluctuations in temperature and humidity are so big that the result is not good as far as film size stability is concerned.
(C) The conventional method has a further short-coming in that the film size stability of the first film differs from that of the last one because of the change of the drying condition due to evaporation of water from films.